Pierre-Antoine Dubos- PhD - HDR
- Professor (Associate) at Nantes Université
Pierre-Antoine Dubos
- PhD - HDR
- Professor (Associate) at Nantes Université
About
70
Publications
7,622
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Introduction
I work on the relationships between the shaping, mechanical behavior and resulting microstructures of metallic materials. In particular, I'm interested in the evolution of the microstructure of metals undergoing plastic deformation during thermo-mechanical stress or forming processes. The aim is to study the behavior of these materials experimentally, at different scales, in order to feed numerical calculation codes and be able to predict possible problems during forming or in-service stresses.
Current institution
Additional affiliations
September 2016 - present
September 2013 - August 2016
Education
September 2010 - September 2013
September 2004 - June 2010
Publications
Publications (70)
This study examines the microstructural evolution, phase transformation, and corrosion behavior of 304L stainless steel after 50% cold rolling and annealing within a temperature range of 400–850 °C. X‐ray diffraction, scanning electron microscopy, and cyclic potentiodynamic polarization in 0.6 M NaCl are employed for analysis. Cold rolling induces...
Phase transformations in cold-rolled (CR) 304L austenitic stainless steel were studied using different techniques, including dilatometry, X-ray diffraction and scanning electron microscopy. During continuous annealing, the dilatometric measurements indicated that the evolution of the deformed microstructures led to an important anomaly constituted...
Additive manufacturing processes and especially the family of laser powder bed fusion technologies have a great industrial potential since it enables, from metal powder beds, to produce full density complex monolithic parts. The high-temperature gradient resulting from the locally concentrated energy input leads to strong temperature fields driving...
The objective of this paper is to contribute to a better understanding of the deformation mechanisms of a rolled polycrystalline cobalt sheet. In order to achieve this goal, a particular attention is given to the strain-induced phase transformation and the forming parameters on which it may depend such as the plastic anisotropy or the loading path....
The sequence of structural changes produced in two deformed microstructures of austenitic stainless steel elaborated by a multipass unidirectional cold rolling (CR) and a two‐step one, to a 75% thickness reduction, is followed by dilatometric experiments. The two materials show different dilatometric behaviors. X‐ray diffraction and microhardness m...
Plastic deformation of titanium alloys depends on the temperature and the mechanical loading mode. It is accommodated by a complex mixture of slip and twinning systems. It remains nevertheless unclear which deformation modes are activated in the polycrystal during loading, especially with the temperature. To better understand the mechanical behavio...
Le cobalt polycristallin est un métal de structure hexagonale compacte (HC) qui présente un rapport c/a proche de celui d’une structure compacte idéale et une énergie de faute d’empilement faible, lui conférant des mécanismes de déformations particuliers. Dans cette étude, le comportement mécanique d’une tôle de 500 μm d’épaisseur brute de laminage...
Uniaxial tensile tests were carried out on nickel sheets containing only few grains across the thickness thus presenting a so-called multicrystalline state. Pristine sheets used as reference and substrates covered by a nickel layer deposited by physical vapor deposition (magnetron sputtering) were studied. Results attest that the surface treatment...
La détérioration des propriétés mécaniques de tôles de nickel ne présentant que quelques grains dans l'épaisseur (état multicristallin) est liée au retardement de l'activation des mécanismes de déformation dans les grains surfaciques tronqués. Des dépôts physiques en phase vapeur, par pulvérisation cathodique magnétron, d'un matériau sur un substra...
Le comportement mécanique de pièces miniaturisées est analysé au travers d'une étude de la loi de Hall-Petch pour différents matériaux dans des conditions de températures variables. Ces travaux ont permis de mettre en évidence une contrainte d'écoulement réduite par rapport à celle attendue par la loi de Hall-Petch pour les échantillons possédant p...
This paper develops a simple and versatile analytical method for characterizing residual stress associated with the deposition of thick, thin, single and multilayer coatings. This study is of great importance, since the generation of residual stress can lead to the formation of significant defects in the coating. To illustrate the effectiveness of...
The allotropic phase transformation in polycrystalline high-purity cobalt is incompletely reversible and exhibits a temperature hysteresis. This leads to the presence of a FCC metastable phase at room temperature, which alters the mechanical properties. Moreover, this phase transformation seems to be induced by the plastic deformation. The influenc...
Mechanical properties in tension of cobalt have been studied in a wide range of grain size d using thickness t of samples from 125 to 700 μm. The Hall and Petch (HP) relationship indicates that the yield stress strongly varies for t/d below a critical value around 14, highlighting the existence of a multicrystalline regime. The behavior becomes alm...
L’effet de la microstructure et du chargement thermomécanique sur les transformations de phases du cobalt polycristallin de haute pureté (99,9 %) a été investigué via diverses techniques expérimentales. Les recuits thermiques permettent une homogénéisation de la microstructure sans provoquer l’achèvement de la transformation martensitique. La trans...
Thermal and mechanical effects on the phase transformation of polycrystalline two-phase HCP/FCC cobalt have been studied in coupled and decoupled ways. This experimental work has involved in situ X-ray and neutron diffraction analysis to determine phase proportions under various thermomechanical conditions, those which are not referenced in the lit...
Institut Laue-Langevin (ILL) Large Facility
Neutron diffraction is a powerful non-destructive volumetric evaluation method for the analysis of the internal stress state in components processed by Laser Powder Bed Fusion (LPBF). High cooling rates and heterogeneous distribution of temperature during additive manufacturing lead to large residual stress fields. Residual stresses developed durin...
Reducing the CO2 emissions is one of the major objectives in aerospace engineering. In this regard, XSun startup is developing an autonomous solar drone, SolarXOne. The latter is independent on one hand in decision with an autopilot and on the other hand in energy using solar cells and batteries. This paper aims at presenting the mechanical behavio...
This work investigates the effect of relative humidity (RH) and temperature on drying phenomenon of a siloxane coating during the sol-gel process. An experimental approach was taken, due to a lack of available data in existing literature. Dynamic Vapor Sorption, Fourier Transform Infra-Red spectroscopy and X-ray Photoelectron Spectroscopy analyses...
Les peintures sont classiquement utilisées dans le domaine des énergies marines renouvelables pour protéger les structures acier de la corrosion. Afin d’améliorer l’adhérence et donc la durabilité de ces revêtements, des traitements de surface peuvent être employés. Habituellement, celui-ci est réalisé par sablage. Dans cette étude, des traitements...
To reduce maintenance and to increase the corrosion protection and lifetime of maritime
structures while complying with environmental standards, multilayer coatings are applied to protect steel sections. A new generation of hybrid sol-gel and/or HiPIMS Ni-based thin films appear to constitute an efficient pre-treatment before the anti-corrosion pai...
The occurrence of size effects in cobalt was examined by the analysis of mechanical properties of samples with thickness t, in a large range of grain size d giving a number of grains across the thickness t/d. On Hall-Petch plots, from the very beginning of plastic strain, two linear behaviors are notable: the polycrystalline one for higher t/d and...
Miniaturization of small metallic systems can lead to a softening of the mechanical behavior due to the reduction of scale. Size effects have been considerably studied recently for materials with various crystallographic structures. Under tensile conditions, thin specimen exhibit softer mechanical properties when the number of grains across thickne...
The purpose of this paper is to emphasize the improvement of Zr-based ceramics properties as a function of addition of Ce ions in the structure of the original ceramics. The structural investigations proposed in this paper cover X-ray, and neutron diffraction offered the first indication of the variation of the phase composition and the structural...
In this work experimental tensile tests were performed on a DP1000 steel at different temperature levels in the range (293-600) K. This experimental database was used for the identification of a Johnson-Cook constitutive model taking into account temperature effects. A critical void area fraction and a corresponding critical equivalent plastic stra...
The mechanical behaviour of face centered cubic metals is deeply affected when specimen dimensions decrease from a few millimeters to a few micrometers. At room temperature, a critical thickness (t) to grain size (d) ratio (t/d)c was previously highlighted, under which the softening of mechanical properties became very pronounced both in terms of H...
The mechanical behaviour of polycrystalline hexagonal close packed cobalt was investigated over a large range of grain size d in order to examine the occurrence of size effects. Crystallographic texture and amount of face centered cubic allotropic phase were maintained unchanged thanks to appropriate heat treatment procedures. The Hall-Petch (HP) r...
The thermomechanical behavior of polycrystalline sheets of high purity copper with various numbers of grains (d) across the thickness (t) is experimentally analyzed. As for other face centered cubic materials, the t/d ratio strongly affects the work hardening of copper, especially for t/d values lower than a critical one around five. These results...
Influence of the size effects on the mechanical behavior of face-centered cubic metals was studied for complex loadings close to microforming ones. The effect of a reduction in thickness (t) over grain size (d) ratio on the mechanical behavior for high-purity nickel and copper is investigated for three different loadings by tensile and Nakazima tes...
To increase the ductility of bimetallic wires after deep drawing process, annealing is generally performed, leading to the diffusion between both metals. This paper focuses on the microstructural and thermokinetic properties of copper clad aluminium wires in order to optimise their process and properties. Solid state diffusion reaction was carried...
Thèse de doctorat présentée et soutenue le : 28/10/2013 par Pierre-Antoine Dubos pour obtenir le Spécialité : Mécanique des Solides, des Matériaux et des Structures Influence de la température et du trajet de chargement sur les transitions volume/surface des métaux cubiques à faces centrées Directeur de thèse : Eric Hug Jury M.
Etude sur les effets de taille lors la mise en forme du nickel de haute pureté caractérisés par le nombre de grains dans l’épaisseur de la tôle
Textured alumina ceramics were obtained by Spark Plasma Sintering (SPS) of
undoped commercial a-Al2O3 powders. Various parameters (density, grain growth,
grain size distribution) of the alumina ceramics, sintered at two typical
temperatures 1400{\deg}C and 1700{\deg}C, are investigated. Quantitative
textural and structural analysis, carried out usi...
The influence of the size effects on the forming processes for micro-sized parts is not yet well known. This work follows experimental and numerical studies of the effect of a reduc-tion in thickness (t) over grain size (d) ratio on the mechanical properties of high purity copper. Under tensile conditions, copper exhibits softer mechanical properti...
